Several different wireless communication techniques have been developed, including frequency division multiple access (FDMA), time division multiple access (TDMA) and various spread spectrum techniques. One common spread spectrum technique used in wireless communication is code division multiple access (CDMA) signal modulation in which multiple communications are simultaneously transmitted over a spread spectrum radio-frequency (RF) signal. Several mobile communication protocols use CDMA signal modulation, such as the CDMA family of standards and wideband CDMA (W-CDMA) family of standards.
Conserving power in a wireless communication device (WCD) is a paramount concern, as the WCD is typically powered by limited battery resources. To conserve power, the WCD may periodically operate in a low-power mode, often referred to as “standby” mode. When operating in standby mode, the wireless communication device reduces power consumption by disconnecting power to selected internal components. Slotted paging techniques have been developed, in which paging signals are sent from a base station to WCDs within assigned paging slots, separated by predetermined intervals of time. Slotted paging allows a WCD to operate in standby mode during the period of time between consecutive paging slots without missing paging signals.
When a WCD device operates out of service, however, the wireless communication device is unable to receive any service signals from base stations. An out-of-service condition may occur upon initial power-up or upon a loss of service during normal operation. In either case, the WCD is unable to operate in standby mode as it does not know when or in which frequency band to look for paging signals. Instead, the WCD constantly searches for a service signal in both frequency and code space. A constant search state substantially increases power consumption and quickly drains battery resources in the WCD.